Attention is highly critical to our conscious experience. A failure to focus or to shift attention can be devastating, and may contribute to neurological and psychiatric diseases such as attention deficit hyperactivity disorder (ADHD), dyslexia, and schizophrenia. Experiments from the Desimone lab and others have shown that attention alters neural activity in many visual areas and synchronizes activity across brain regions. There is increasing evidence for the presence of top-down modulatory mechanisms mediating attention. However, the precise neural circuitry underlying these effects is largely unknown, and it remains difficult to establish causal links between activities in specific neural circuits or cell types, and emergent behaviors and pathologies. Accordingly, I will develop the use of the technologies for activating and silencing specific types of neurons with millisecond-timescale precision in the primate brain, with which to perform a time- resolved analysis of necessity and sufficiency of specific prefrontal neural activity patterns hi mediating top- down control of attention. During the mentored phase of this grant, Dr. Robert Desimone is the mentor and Dr. Edward Boyden is a collaborator. Dr. Robert Desimone is a leader in the field of attention and has established many of its fundamental and novel concepts. Dr. Edward Boyden is a pioneer in neurotechnology development, having developed optical methods for controlling neurons and is continuously contributing novel concepts about how to engineer tools to facilitate the exploration of the brain. During the mentored phase of this grant, I will continue to perfect my skills in experimental design, conduction and analysis, and continue to learn how to manipulate specific neural substrates in the densely-wired 3-dimensional primate brain. By working between multiple disciplines, I will learn critical communication and management skills important for the interdisciplinary work of the twenty-first century.